1. Technical Field
This invention relates generally to pneumatic control systems, and more particularly to a multi-pressure pneumatic control system for industrial air applications wherein a selective plurality of sequential and repetitive air pressures are required, as in the control of welding apparatuses and similar applications.
2. Background Information
A large number of the welding guns used in industry at the present time are of the backup type, and they are carried on robot arms for moving them between selected work stations, and for manipulating them at a plurality of work stations. A backup type welding gun employs a double air cylinder construction wherein a weld cylinder is formed in a position piston which is operatively mounted in a positioning cylinder, which may also be termed a backup cylinder. Operatively mounted in the weld cylinder is a weld cylinder rod and its coacting weld piston, which are extended and retracted by pressurized air, to and from an operative welding position at a work station. Due to the inherent structure of a backup type welding gun, and the fact that its internal movable parts are operated by pressurized air, there exists a problem of lost welding time because of the long positioning time involved in extending the combination position piston and weld cylinder to an operative position for a welding operation after the welding gun has been moved from one work station to another.